Oscillating Stress on Viscoelastic Behavior of Thermoplastic Polymers

2000 ◽  
Vol 122 (3) ◽  
pp. 386-389 ◽  
Author(s):  
Rudolph J. Scavuzzo
Keyword(s):  
Mechanical Vibration ◽  
Viscoelastic Behavior ◽  
Tensile Tests ◽  
Rotating Machinery ◽  
Rapid Decrease ◽  
Mean Stress ◽  
Permanent Set ◽  
Cyclic Stresses ◽  
Standard Specimens ◽  
Bending Stresses

Polymers are used in many applications where they are subjected to cyclic stresses. PVC and HDPE piping are often used in systems that include rotating machinery that cause mechanical vibration. Recent testing of thermoplastics indicates that there may be a large effect on the viscoelastic strains of thermoplastics from oscillating stresses. Cyclic loading on the permanent set of cross-linked elastomers has been studied. Perhaps, as expected, the effect of the oscillating behavior is measurable. Two types of tests have been conducted. First, tensile tests on HDPE standard specimens were conducted where oscillating stresses were superimposed onto an initial static or mean stress. These measurements showed a rapid decrease in the oscillating stresses when compared to measurements when steady nonoscillating stresses are applied to the same type of specimen. In the second test series, pressurized HDPE piping was subject to oscillating bending stresses. Ratcheting of the hoop strains in the pipe occurs. Results show that these strains follow the constitutive relationships of linear viscoelasticity and experimental results imply that viscoelastic changes are accelerated by stress oscillations. These preliminary results seem to indicate that the effects of oscillating stresses on the viscoelastic behavior of thermoplastics may be significant. A systematic study is required to further understand this behavior. [S0094-9930(00)02403-3]

scholarly journals Influence of Mechanical Vibration Moulding Process on the Tensile Properties of TiC Reinforced LM6 Alloy Composite Castings

2011 ◽  
Vol 66-68 ◽  
pp. 1207-1212 ◽  
Author(s):  
Mohd Sayuti ◽  
Shamsuddin Sulaiman ◽  
B.T. Hang Tuah Baharudin ◽  
M.K.A.M. Arifin ◽  
T.R. Vijayaram ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Titanium Carbide ◽  
Tensile Properties ◽  
Mechanical Vibration ◽  
Weight Fraction ◽  
Tensile Tests ◽  
Alloy Matrix ◽  
Remarkable Effect ◽  
Moulding Process ◽  
Particulate Reinforced

Vibrational moulding process has a remarkable effect on the properties of castings during solidification processing of metals, alloys, and composites. This research paper discusses on the investigation of mechanical vibration mould effects on the tensile properties of titanium carbide particulate reinforced LM6 aluminium alloy composites processed with the frequencies of 10.2 Hz, 12 Hz and 14 Hz. In this experimental work, titanium carbide particulate reinforced LM6 composites were fabricated by carbon dioxide sand moulding process. The quantities of titanium carbide particulate added as reinforcement in the LM6 alloy matrix were varied from 0.2% to 2% by weight fraction. Samples taken from the castings and tensile tests were conducted to determine the tensile strength and modulus of elasticity. The results showed that tensile strength of the composites increased with an increase in the frequency of vibration and increasing titanium carbide particulate reinforcement in the LM6 alloy matrix.

Nonlinear Viscoelastic Analysis of Double Base Propellant

2012 ◽  
Vol 591-593 ◽  
pp. 1147-1151
Author(s):  
Jin Sheng Xu ◽  
Yu Tao Ju ◽  
Chang Sheng Zhou
Keyword(s):  
Viscoelastic Behavior ◽  
Tensile Tests ◽  
Nonlinear Material ◽  
Creep Recovery ◽  
Model Parameters ◽  
Fe Model ◽  
Nonlinear Viscoelastic ◽  
Constant Rate ◽  
Displacement Based ◽  
Double Base

This study presents the characterization of the nonlinearly viscoelastic behavior of double base propellant (DBP) using Schapery-type constitutive model in the different conditions of temperature, strain level and strain rate. A recursive-iterative numerical algorithm is generated for the Schapery-type nonlinearly viscoelastic constitutive and implemented in a displacement-based finite element (FE) code for ABAQUS user material subroutines. Then, the model parameters are obtained by analyzing the response of creep-recovery tests and constant rate tensile tests at different temperatures, strain levels and strain rates. And find a linear relationship between temperatures and the effective stresses which determine the limit of linear viscoelactic. The FE model with the calibrated time-dependent and nonlinear material parameters is used to simulate the creep-recovery tests and the constant rate tensile tests, and reasonable predictions are shown.

Thermal Shock Effect of Nano-TiO2 Enhanced Glass Fiber Reinforced Polymeric Composites: An Assessment on Tensile and Thermal Behavior

2020 ◽  
Vol 978 ◽  
pp. 277-283
Author(s):  
Kishore Kumar Mahato ◽  
Krishna Chaitanya Nuli ◽  
Krishna Dutta ◽  
Rajesh Kumar Prusty ◽  
Bankim Chandra Ray
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Glass Fiber ◽  
Thermal Shock ◽  
Viscoelastic Behavior ◽  
Stress Transfer ◽  
Tensile Tests ◽  
Fiber Reinforced ◽  
Glass Fiber Reinforced ◽  
Service Period

Fiber reinforced polymeric (FRP) composite materials are currently used in numerous structural and materials related applications. But, during their in-service period these composites were exposed to different changing environmental conditions. Present investigation is planned to explore the effect of thermal shock exposure on the mechanical properties of nanoTiO2 enhanced glass fiber reinforced polymeric (GFRP) composites. The samples were conditioned at +70°C temperature for 36 h followed by further conditioning at – 60°C temperature for the similar interval of time. In order to estimate the thermal shock influence on the mechanical properties, tensile tests of the conditioned samples were carried out at 1 mm/min loading rate. The polymer phase i.e. epoxy was modified with different nanoTiO2 content (i.e. 0.1, 0.3 and 0.5 wt. %). The tensile strength of 0.1 wt.% nanoTiO2 GFRP filled composites exhibited higher ultimate tensile strength (UTS) among all other composites. The possible reason may be attributed to the good dispersion of nanoparticles in polymer matrix corresponds to proper stress transfer during thermal shock conditioning. In order to access the variations in the viscoelastic behavior and glass transition temperature due to the addition of nanoTiO2 in GFRP composite and also due to the thermal shock conditioning, dynamic mechanical thermal analysis (DMTA) measurements were carried out. Different modes of failures and strengthening morphology in the composites were analyzed under scanning electron microscope (SEM).

Heat-Treated Microstructure and Mechanical Properties of TC4 Alloy

2011 ◽  
Vol 197-198 ◽  
pp. 1524-1527 ◽  
Author(s):  
Hong Bo Dong ◽  
Xin Yang
Keyword(s):  
Mechanical Properties ◽  
Solution Treatment ◽  
Tensile Tests ◽  
Double Shear ◽  
Comprehensive Properties ◽  
Α Phase ◽  
Microstructure And Mechanical Properties ◽  
Heat Treated ◽  
Standard Specimens ◽  
Tc4 Alloy

The effects of heat treatment process on the microstructure and mechanical properties of TC4 alloy were investigated. The double shear and tensile tests were carried out by using the 12mm diameter standard specimens after solution treatment at 520°С for 1.5h and water quenching, followed by aging at 480-540°С for 8h. The microstructure and facture surface were analyzed using the equipment of metallurgical microscope and scanning electron microscopy. The results show that TC4 alloy show the best comprehensive performances after solution treatment at 940°С for 1.5h, aging at 520°С for 8h; the tensile specimens display a typical ductile fracture with oval dimples of various sizes; the microstructures with clear grain boundary and obvious lamellar structure are observed at room temperature. It indicates that the excellent comprehensive properties can be obtained by controlling the grain size of primary α phase and the morphology structure and amount of the secondary α phase at optimized aging temperature.

scholarly journals Thermoplastic elastomers containing 2D nanofillers: montmorillonite, graphene nanoplatelets and oxidized graphene platelets

2015 ◽  
Vol 17 (4) ◽  
pp. 74-81 ◽  
Author(s):  
Sandra Paszkiewicz ◽  
Iwona Pawelec ◽  
Anna Szymczyk ◽  
Zbigniew Rosłaniec
Keyword(s):  
Tensile Modulus ◽  
Thermoplastic Elastomer ◽  
Tensile Tests ◽  
Thermoplastic Elastomers ◽  
Graphene Nanoplatelets ◽  
Soft Phase ◽  
Permanent Set ◽  
Transmission Electron ◽  
Tetramethylene Oxide

Abstract This paper presents a comparative study on which type of platelets nanofiller, organic or inorganic, will affect the properties of thermoplastic elastomer matrix in the stronger manner. Therefore, poly(trimethylene terephthalate-block-poly(tetramethylene oxide) copolymer (PTT-PTMO) based nanocomposites with 0.5 wt.% of clay (MMT), graphene nanoplatelets (GNP) and graphene oxide (GO) have been prepared by in situ polymerization. The structure of the nanocomposites was characterized by transmission electron microscopy (TEM) in order to present good dispersion without large aggregates. It was indicated that PTT-PTMO/GNP composite shows the highest crystallization temperature. Unlike the addition of GNP and GO, the introduction of MMT does not have great effect on the glass transition temperature of PTMO-rich soft phase. An addition of all three types of nanoplatelets in the nanocomposites caused the enhancement in tensile modulus and yield stress. Additionally, the cyclic tensile tests showed that prepared nanocomposites have values of permanent set slightly higher than neat PTT-PTMO.

scholarly journals Contribution of glycosaminoglycans to viscoelastic tensile behavior of human ligament

2009 ◽  
Vol 106 (2) ◽  
pp. 423-431 ◽  
Author(s):  
Trevor J. Lujan ◽  
Clayton J. Underwood ◽  
Nathan T. Jacobs ◽  
Jeffrey A. Weiss
Keyword(s):  
Viscoelastic Properties ◽  
Viscoelastic Behavior ◽  
Tensile Tests ◽  
Tissue Level ◽  
Collagen Fibrils ◽  
Material Behavior ◽  
Structural Failure ◽  
Extracellular Matrix Molecules ◽  
Before And After ◽  
Different Levels

The viscoelastic properties of human ligament potentially guard against structural failure, yet the microstructural origins of these transient behaviors are unknown. Glycosaminoglycans (GAGs) are widely suspected to affect ligament viscoelasticity by forming molecular bridges between neighboring collagen fibrils. This study investigated whether GAGs directly affect viscoelastic material behavior in human medial collateral ligament (MCL) by using nondestructive tensile tests before and after degradation of GAGs with chondroitinase ABC (ChABC). Control and ChABC treatment (83% GAG removal) produced similar alterations to ligament viscoelasticity. This finding was consistent at different levels of collagen fiber stretch and tissue hydration. On average, stress relaxation increased after incubation by 2.2% (control) and 2.1% (ChABC), dynamic modulus increased after incubation by 3.6% (control) and 3.8% (ChABC), and phase shift increased after incubation by 8.5% (control) and 8.4% (ChABC). The changes in viscoelastic behavior after treatment were significantly more pronounced at lower clamp-to-clamp strain levels. A 10% difference in the water content of tested specimens had minor influence on ligament viscoelastic properties. The major finding of this study is that mechanical interactions between collagen fibrils and GAGs are unrelated to tissue-level viscoelastic mechanics in mature human MCL. These findings narrow the possible number of extracellular matrix molecules that have a direct contribution to ligament viscoelasticity.

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